Inhibition of foaming in steam generators



nited ITION F FOAMING IN STEAM GENERATORS No Drawing. ApplicationDecember 21, 1946, Serial No. 717,822

7 Claims. (Cl. 252321) The present invention relates to antifoamingcompositions which are used in steam boilers and similar steamgenerators, evaporators, etc., to overcome the tendency of the watertherein to foam and hence to bring about the priming of the steamgenerator or the like.

This application is a continuation-in-part of our copending applicationSerial No. 436,489, filed March 27, 1942, now abandoned.

it is well known in the operation of steam boilers, such as in electricpower plants, railroad locomotives and the like, or in evaporators, thatthe Water therein, even though initially it shows very little tendencyto foam, will, when the amount of total solids therein approaches arelatively high concentration, develop a very decided tendency to foam.When this occurs, considerable quantities of water are physicallycarried out of the boilers or evaporators with the steam, thus appearingin the steam lines and in the eventual condensate. Such priming has manydisadvantages because it tends to contaminate the steam lines, to plugor corrode the valves, and under serious conditions may even impair thecylinders and piston rods of the steam engines, or the impeller bladesof turbines in which the steam is used for the generation of power.

Attempts have been made in the past to control this foaming, byexcessive blowdown of the boilers or by the injection thereinto of suchmaterials as castor oil, tallow, and the like. While these fattymateriols have some small degree of efiiciency, they are, on the otherhand, quite deficient in that they introduce new difficulties which, insome instances, are worse than the conditions they are intended to cure.In the first place, these fatty acids or glycerides are unstable underthe conditions existing in the boilers, particularly as the pressure andtemperature increase, the high temperatures leading to rapiddecomposition of the glycerides, which, if anything, will tend toincrease the foaming and priming difiiculties. Furthermore, in manyinstances certain of the decomposition products thus produced, orsometimes even the materials themselves, have a definite volatility withsteam and will, therefore, steam-distil out of the boilers, thusappearing in the steam and in the condensate. This, of course, is alsovery undesirable. Furthermore, such types of antifoaming agents usuallyhave to be employed in relatively large quantities, adding not only tothe expense but also to the inconvenience of operating the steamgenerators; and those which have a tendency to decompose do so quiterapidly, and hence their effectiveness is of short duration, whichtherefore necessitates the continual charging into the boilers or othersteam generators of relatively large amounts of these older antifoamingagents. Moreover, such antifoaming agents are difiicult to use becausethe amounts in which they are efficacious are very critical, and anyoverdosage usually aggravates the difficulty instead of curing it.

One of the objects of the present invention is the preparation of aliquid suitable for the generation. of steam in steam generators andcomprising water contates atent however, be of high molecular tainingdispersed therein a very small amount of a specific type of compoundwhereby, when such water is heated to ;the boiling point in a steamboiler or other generator, being thereby evaporated, the concentrationof solids therein will not bring about excessive foaming and theresulting priming, the added compound being substantially non-volatilewith the steam and stable, so that it will be retained by the Water andneither it nor its decomposition products will appear in the steam andthe resulting condensation thereof.

Another object of the invention is to provide antifoaming compositionsfor employment in steam generation which are readily dispersed in thewater from which the steam is formed. Other objects will appearhereinafter.

In accordance with the invention it has been discovered that there is aseries of compounds which may be broadly designated as symmetricalunsaturated diacylated polyamines where at least one of the acyl groupscontains at least one carbon to carbon double bond and which are of ahigh order of efliciency when used as antifoaming and antipriming agentsin steam generators operating under superatmospheric pressureconditions! These symmetrical unsaturated diacyl derivatives must,weight and should possess certain limiting characteristics as regardsmolecular size, as hereinafter more fully described.

Fundamentally speaking, the compounds involved in the practice of thepresent invention can be illustrated by the structural formula:

XC-NY-N-OZ ll I I i (l in which X and Z each represents a group selectedfrom the class consisting of aliphatic hydrocarbon and hydroxy aliphatichydrocarbon groups each containing at least 10 carbon atoms and at leastone of the radicals X and Z containing at least one carbon to carbondouble bond, and Y is the residue from a polyamine selected from thegroup consisting of the monoalkylene diamines and the polyalkylenepolyamines. Typical acids from which the acyl groups may be derived areundecylenic (X and/or Z=l0 carbon atoms), oleic, ricinoleic (X and/orZ=l7 carbon atoms), and erucic (X and/or Z=21 carbon atoms).

The total molecular weight of the condensation prod ucts as well as thespatial configuration and the unsaturation of the radicals X and/or Z inthe above identified formula apparently has a marked effect on theireflicacy as antifoaming and antipriming agents.

The compounds employed for the purpose of the invention have twoterminal acyl groups which are substantially equal as regards the numberof carbon atoms in each. These derivatives are, therefore, referred toas symmetrical. In the practice of the invention the total number ofcarbon atoms in the derivative must be at least 26 carbon atoms.

The preferred compounds for the purpose of the invention are the diacylpolyalkylene polyamines in which the acyl radicals are either oleylgroups or ricinoleyl. These compounds are prepared preferably byreacting oleic acid or ricinoleic acid or their glyceryl esters with apolyalkylene polyamine such as, for example, diethylenetriamine,triethylenetetramine, tetraethylenepentamine,

- or the corresponding polypropylene polyamines, in proportions of about2 mols of the fatty acid for each mol of the polyalkylene polyamine. Thepreferred compounds contain from 38 to 50 carbon atoms.

It will be recognized that the polyalkylene polyamines contain bothprimary and secondary amino groups and that there is a possibility ofsome acylation of the secondary amino groups. The principal productsobtained,

Patented Sept. 13, 1955.

however, are those in which both of the terminal primary amino groupsare acylated with very little, if any, acylation of the secondary aminogroups.

We shall describe hereinbelow the preparation of several'of thematerials, and'while the examples disclose a few of many satisfactorypreparative procedures, in most cases the same product may be obtainedby more than one route.

The most used method of preparation involved the use of the acid and theamine, in nearly theoretical amounts for the product'desired,and'consisted essentially in the initial formation of the amine salt ofthe acid, followed by dehydration to theamide by heating. In certaincases, the use of the acid. halide was resorted to in order to introducean acyl group. In still another very useful procedure, the fatty acidester was used instead of the acid itself. Thus, while any usual estercan be used, such as methyl, ethyl, glycol, etc., the glycerides of thehigh molecular weight acids are often very readily obtainable and werethe subject of much of'the preparative work.

By' heating the glyceride andth'e polyamine together in the properproportions, the alkyline amine causes the ester to be split, liberatingthe fatty acid, which then reacts with theamine to give the amide.Usually, when using the triglycerides, such proportions were used thattwo of the three acid chains would be split off from the ester and used,and the remaining fatty acid rnono glyceride remained in the product asa harmless byproduct. However, excellent materials have also been formedwhere the proportion of triglyceride or other ester used was such thatall the available acyl chains were used in forming the amide. Indeed,the reaction of theoretical amounts of a polyethylene polyamine and aglycerol monoester has yielded useful products.

The number of different compounds which can be prepared is quitenumerous, and while we are giving a large number of examples, we do notwish to be limited to those specifically described nor to the speciesclaimed. These examples are as follows:

Example I A mixture of 19.8 grams of oleic acid and 3 grams of a 60%aqueous solution ofethylenediamine was heated with stirring at 150degrees C. to 160 degrees C. for 3 hours, after more cautious initialheating for the removal of the bulk of the water. The product, whencool, was a brown wax.

Example 11 A mixture of 141 grams of oleic acid and 36.5 grams oftriethylenetetramine was stirred and heated at 150 degrees C. .to 160degrees C. for 3 hours. When cool, the product was a yellow-brown wax.

Example III A mixture of 20.9 grams of ricinoleic acid and 4.4 grams oftriethylenetetramine was heated with stirring at 150 degrees C. to 160degrees C. for 3 hours. When cool, the resulting product was a darkbrown, viscous oil.

Example IV A mixture of 22.6 grams of oleic acid and 4.1 grams ofdiethylenetriarnine was heated with stirring for 3 hours at 150 degreesC. to 160 degrees C.. When cool, the product was a low-melting brownwax.

Example V A mixture of 28 grams of castor oil and 4.4 grams oftriethylenetetramine was heated with stirring at 150 degrees C. to 160degrees C. for 4 hours. When cool, the product was a very viscous brownoil.

Example VI A mixture of 31 grams of commercial olein (oleo oil) and 5.1grams of triethylenetetramine was stirred and heated at 150 degrees C.to 160 degrees C. for 4 hours. When cool, the product was a brown wax.

4 Example VII A mixture of 30 grams of olive oil and grams oftriethylenetetramine was heated with stirring at 150 degrees C. to 160degrees C. for 4 hours. When cool, the product was a light brown, softwax.

Example VIII A mixture of grams of neats-foot oil and 5 grams oftriethylenetetramine was heated with stirring at degrees C. to degreesC. for 4 hours. When cool, the product was a brown wax.

Example IX Example X A mixture of 11.3 grams of oleic acid and 4.1 gramsof diethylenetriamine was heated with stirring at 150 degrees C. to 160degrees C. for 2 hours. Then 10.7 grams of commercial stearic acid wasadded and the process continued another 2 hours. When cool, the productwas a brown wax.

Example XI A mixture of 280 grams of No. 3 grade commercial castor oiland 66 grams of triethylenetetramine was heated with stirring at 150degrees C. to 160 degrees C. for 3 hours. When cool, the product slowlysolidified to a light yellow wax.

Example XII A mixture of 23.8 grams of butyl acetylricinoleate and 4.4grams of triethylenetetramine was treated like the mixture of ExampleXI. The cooled product was a clear, brown, viscous oil.

Example XIII A mixture of 17.7 grams of glycol oleate and 4.4 grams oftriethylenetetramine was treated like the mixture of Example XI. Thecooled product was a brown wax.

Example XIV A mixture of 18.1 grams of propylene glycol oleate and 4.4grams of triethylenetetramine was treated like the mixture of ExampleXI. When cool, the product was a brown grease.

Example XV A mixture of 6 parts of soybean oil and 1 part oftriethylenetetramine was processed by heating with stirring at 150degres C. to 160 degrees C. for 3 hours.

Example XVI A mixture of 6 parts of raw linseed oil and 1 part oftrlethylenetetramine was processed as in Example XV.

Example XVII A mixture of 6 parts of hempseed oil and 1 part oftr1ethylenetetramine was processed as in Example XV.

Example XVIII A mixture of 6 parts of sunflower oil and 1 part oftriethylenetetramine was processed as in Example XV.

Example XIX A mixture of 6 parts of sesame oil and 1 part oftriethylenetetramine was processed as in Example XV.

Example XX A mixture of 6 parts of perilla oil and 1 part oftriethylenetetramine was processed as in Example XV.

Example XXI A mixture of 6 parts of palm oil and 1 part oftriethylenetetramine was processed as in Example XV.

Example XXII A mixture of 20.3 grams of erucic acid and 3 grams of a 60%aqueous solution of ethylenediamine was stirred and heated at 150degrees C. to 160 degrees C. for 3 hours, after more cautious initialheating to remove the bulk of the water. When the product was cool, itwas a brown Wax.

It will be recognized that various types of unsaturated fatty acids arepresent in the various oils described in the examples. Some of thesefatty acids contain a single carbon to carbon double bond and otherscontain two or more carbon to carbon double bonds. In general, thosefatty acids containing a single carbon to carbon double bond have givenvery good results in the preparation of compounds for the practice ofthis invention.

The number of carbon atoms in the polyamine is subject to variation butis preferably within the range of 2 (e. g., ethylenediamine) to (e. g.,decamethylenediamine) for the monoalkylene polyamines and within therange from 4 (e. g., diethylenetriamine) to 8 (e. g.,tetraethylenepentamine) for the polyalkylene polyamines.

The unsaturated diacyl compounds of the present invention are mucheasier to disperse and to handle than the corresponding saturated diacylderivatives. These compounds, being substantially insoluble in water,ordinarily must be mixed with various other materials to render themreadily dispersible, and they preferably should be handled in the liquidstate to facilitate such mixing. The higher the temperature. required tomaintain the compounds in a fluid form the greater is the hazard topersonnel in handling them, and the greater are the chances for thermaldecomposition or oxidation of the antifoam compounds and the chances forfreezing of lines, pumps, and the like. Furthermore, it has beenrepeatedly observed that the dispersibility of the antifoam compound isbetter when its melting point is low. Ease of initial dispersion of theantifoam mixture and stability of the resultant dispersion so thatseparation of active ingredients does not occur are very important inthe use of antifoams. The following data on melting points of theunsaturated diacyl derivatives herein described as compared withsaturated diacyl derivatives having the same number of carbon atomsshows that the introduction of a single carbon to carbon double bondreduces the melting point by more than one-half:

RING-BALL SOFTENING POINTS OF DIACYLATED POLYETHYLENEPOLYAMINES FattyAcid from Which Acyl Degrees Groups are Derived Amine C.

Diethylenetriamine.

IZ-Hydroxystearim- Ricinoleic This data was obtained by the A. S. T. M.method. 13-28-391.

The products hereinabove described, while not ordinarily considered assoluble in water to any great extent, may be suitably dispersed in wateror emulsified therewith, so that effective amounts thereof may beintroduced and be present in the water Within the steam generator underoperating conditions. The emulsifying or dispersing agent used must,however, be of a kind that does not cause foaming, either by itself orby its decomposition products. The compounds may be used conjointly witheach other as well as with other known antifoaming agents, such as, forexample, castor oil.

The amounts of these high-molecular-weight diacyl derivatives ofpolyamines which are required are extremely small, and in general onegrain per gallon is 6 ample. For many purposes, however, amounts ofaslittle as g grain per gallon in the feed water will still givevaluable results, and the amounts may be even further reduced. Forexample, grain per gallon of this type of condensation product willsuppress foam in a boiler for from 15 to 20 minutes. Comparing this withthe efficacy of castor oil used on the order of grain per gallon, whichwill suppress the foam for only about 30 seconds to one minute, it isobvious that if one were to use castor oil it would have to becontinuously fed into the boiler, with the unavoidable accumulation inthe boiler of a lot of soap produced by the reaction of the liberatedfatty acids with the alkali present in the water, which would onlyaggravate the problem. The diacyl derivatives under discussion, however,are quite stable and do not yield undesirable by-products.

A comparison of castor oil with the material described above in ExampleIV showed that, while 380 parts per billion of castor oil in the feedwater permitted maximum increase of dissolved solids in the boiler waterfrom 154 to 237 grains per gallon, the same amount of the material ofExample IV permitted the dissolved solids in the boiler water toincrease to 2000 grains per gallon without priming or carry-over.

Depending, of course, upon the degree of concentration of solids, thedosage may be varied, but one grain per gallon is about as much as wouldever have to be used even under serious conditions, and for manypurposes 35 grain per gallon and even less can be used. The process isparticularly effective at pressures of about 250 pounds per square inch.

The introduction of the antifoaming compounds of the present inventioninto the boiler may be accomplished in a number of ways. Thus, theantifoaming compositions may be dispersed or physically mixed with, say,sodium carbonate or some other material used for treating the boilerwater and pumped with the feed water into the boiler by means of eitheran injector or a feed water pump. The compounds may also be dissolved insuitable organic Water-miscible solvents such as alcohols, ethers,ketones, etc., and introduced in small measured amounts into the feedWater entering the boiler. Suitable mechanical measuring devices whichwill periodically or continuously inject the required dosage of theantifoaming compounds into the feed water may be used, so that theintroduction will be more or less in proportion to the steam consumptionto which the steam generator is subjected. Another manner of introducingthe antifoaming compounds is to form an emulsion thereof in water andthen feed said emulsion either directly into the boiler or the feedwater lines leading to it. The invention, therefore, is not to belimited by the manner of introduction of the antifoaming composition butrather is to be construed in the terms of the hereunto appended claims.

The preferred active antifoam ingredients are oily to waxy substantiallywater insoluble substances char acterized by stability in hot aqueousalkaline liquids such are used in locomotive boilers and under theconditions which are present in locomotive boilers. Compositionsprepared in accordance with the invention have been demonstrated to beparticularly eifective in locomotive boilers under superatmosphericpressure conditions within the range of to 300 pounds per square inchand the corresponding temperature conditions. Tests have demonstratedthat these compositions are effective even at the much higher pressureand temperature conditions in stationary boilers for power plantoperations, as, for example, superatmospheric pressures up to 1000l500pounds per square inch.

Apart from the fact that the preferred active antifoam ingredientsfunction under severe conditions where other so-called antifoammaterials are ineffective, the reason for the functioning of thesematerials is not known. It has been proven in tests connected with thepractice of this invention that these materials are.very stable tohydrolysis as compared with many other different types of compounds.

The amounts of an antifoam agent employed in inhibiting foam will dependupon several factors, among them the conditions under which the foamoccurs, the amount of foam suppression desired, the percent of solids inthe foaming liquid, the alkalinity, temperature, and pressure of thefoaming liquid, the type and degree of agitation, and the kind of gaspresent in the gas phase of the foam. It is, therefore, impossible tostate any rigid rules for estimating the amount of an antifoam whichneeds to be used. In general, the anti foam will be added in relativelysmall amounts, gradually increasing in size, until the foam iscontrolled to the extent desired.

In the prevention of priming in a power plantor locomotive boileroperating at ordinary pressures, e. g., 250 pounds, it has been foundthat the effective antifoam compositions of this invention, i. e., thosepossessing the requisite molecular size for this use, as explainedabove, are efficient when they are introduced into the feed. water at aconcentration of the order of magnitude of 0.01 grain per gallon, basedon the weight of active antifoam ingredient. Thus, a boiler operating atconcentrations, which is not unusual, would'have- 0.1 grain of activeantifoam per gallon of boiler water. Some foam suppression has beenobtained with only 6 parts by weight of the active ingredient perbillion of water in the feed water going to a boiler. Quantities of from125 to 500 parts by weight of the active ingredient per billion of waterare frequently sufficient merely to improve steam quality. Suchproportions have allowed some users to operate with increaseddissolvedsolids of as much as over the amount permissible without the steamconditioner.

Having thus described the invention, what we claim as new and desire tosecure by Letters Patent of the United States is:

1. A method of generating steam which comprises boiling, undersuperatmospheric pressure conditions,

Water containing an amount of total dissolved solids tending tov producefoaming and priming and a quantity of diricinoleyl triethylenetetramine, said quantity being sufiicient to substantially inhibit saidfoaming, and priming,

2. A method of generating steam which comprises boiling, undersuperatmospheric pressure conditions, water containing an amount oftotal dissolved solids tending to produce foaming and priming and aquantity of dioleyl diethylene triamine, said quantity being sufiicientto substantially inhibit said foaming and priming.

3. A method of generating-'- steam which comprises boiling, undersuperatmospheric pressure conditions, water containing an amount oftotal dissolved solids tending to produce foaming and priming, and afoam inhibiting quantity of asymmetrical unsaturated diacylatedpolyamine in which each acyl group is derived from a fatty acid andcontains atleast 11 carbon atoms and one carbon to carbon double bondand the polyamine is a polyethylene polyamine containing at least 3nitrogen atoms andatleast 4 carbon atoms, the total number of carbonatoms in said unsaturated diacylated polyamine being-within therangefrom 38 to 50.

4. A method of generating steam from a boiler water having a tendency tofoam on boiling which comprises dispersing into said Water a symmetricalunsaturated diacyl polyalkylene polyamine in which the acyl radicals arefrom the group consisting of oleyl and ricinoleyl and the polyamineradical is from the group consisting of diethylenetriamine,triethylenetetramine, and tetraethylenepentamine, said diacylpolyalkylene polyamine being dispersed into saidwater in an amountsufficient substantially to inhibit the tendency of said water to foamon boilingand boiling said water.

5. A method of. generatingsteamfrom a boiler water having a tendency tofoam on boiling which comprises dispersing into said waterdioleyltriethylenetetramine in an amount sufficient substantially toinhibit the tendency of said water to foam on boiling, and boiling saidWater.

6. A method of generating steam'from a boiler water having a tendency-tofoam on boiling which comprisesv dispersinginto said water oleyl stearyldiethylcnetriamine, and boiling said. water.

7. The method of generating steam from a boiler water having a tendencyto foam on boiling which comprises dispersing into said water, in: anamount sufficient to substantially inhibit foaming on boiling, asymmetrical unsaturated diacyl polyethylene polyamine in which eachprimary amino group. is acylated with an unsaturated-fattyacidcontaining at least eighteen carbon atoms, and heating the resultingaqueous dispersion to the boiling point, said acylated polyethylenepolyamine functioning to inhibit the tendency of said water to foam onboiling.

References Cited' in the file'of this patent UNITED STATES PATENTS2,328,551 Gun'derson Sept. 17, 1943 2,345,632 Robinson et al. Apr. 4,1944 2,425,392 Robinson et al. Aug. 12, 1947 2,442,768 Gunderson June 8,1948

7. THE METHOD OF GENERATING STEAM FROM A BOILER WATER HAVING A TENDENCYTO FORM ON BOILING WHICH COMPRISES DISPERSING INTO SAID WATER, IN ANAMOUNT SUFFICIENT TO SUBSTANTIALLY INHIBIT FOAMING ON BOILING, ASYMMETRICAL UNSATURATED DIACYL POLYETHYLENE POLYAMINE IN WHICH EACHPRIMARY AMINO GROUP IS ACYLATED WITH AN UNSATURATED FATTY ACIDCONTAINING AT LEAST EIGHTEEN CARBON ATOMS, AND HEATING THE RESULTINGAQUEOUS DISPERSION TO THE BOILING POINT, SAID ACYLATED POLYETHYLENEPOLYAMINE FUNCTIONING TO INHIBIT THE TENDENCY OF SAID WATER TO FOAM ONBOILING.